Today, I encountered a situation where the company's local area network was partially paralyzed. No problems were found in the core router test. It is estimated that there is a problem with the computer connected to the switch. However, if a similar IP conflict or ARP poisoning occurs on the lower-level switch computer, there should be a record in the routing log. , but nothing is recorded in the log. Patiently observe the indicator lights of the switch, and find that the indicator light corresponding to the computer that cannot access the Internet does not flash, but one indicator light keeps flashing. It is speculated that there is a problem with the computer at this interface. Unplug the network cable of this port, and other indicators start to work normally.
Summary: When there is a problem with the LAN, check the routing log first. If no problem is found, carefully observe the indicator lights of the lower-level switch.